(1) Field of the Invention
The present invention relates to a method for manufacturing an anti-wear slide member having improved anti-pitting and initial stage fit of its slide surface. More specifically, it relates to a treating method for improving an initial stage fit of a slide member for use in an internal combustion engine under especially severe conditions in service and for ameliorating the pitting problem caused by the pores inherent in the sintered alloy. The slide member is manufactured by using the sintered alloy disclosed in U.S. Pat. No. 4,388,144.
(2) Prior Art
As a material for a slide member for use in an internal combustion engine, such as a cam shaft, subjected to sliding, especially under highly plane pressure, ordinary cast iron or a chilled casting of an alloyed cast iron have been employed. For the purpose of improvement in performance, reduction in weight and cost, and so forth, there have been proposed cam-cam shaft assemblies in which the cam piece is made of sintered alloy and the cam shaft is made of steel pipe or the like. Further, a rocker arm pad made of excellent anti-wear material is attached to the rocker arm where it is in contact with the cam piece.
U.S. Pat. No. 4,388,114 discloses a high-density and high-hardness anti-wear sintered alloy characterized by excellent durability for use as a slidable member subjected in service to a relatively high plane pressure, and a method for manufacturing the alloy. The sintered alloy disclosed in this U.S. patent has the advantages that it has extremely excellent anti-wear property and is very strong. These advantages ae at least partially due to the fact that the density of the compression molded mass is increased during sintering. U.S. Pat. No. 4,388,114 also discloses the production of cam shafts and rocker arm pads using such a sintered alloy.
However, since the slide member of this anti-wear sintered alloy has pores generated inherently in the sintered alloy, there remains the problem that pitting takes place on the slide surfaces of the parts after a prolonged sliding time during service under high plane pressure. Further, the parts made of this sintered alloy are inferior in initial stage fit under severe conditions.